Exploited child labour is thought to be behind many counterfeit goods
Up to five people could be charged after a raid on an importer in Exeter, Devon.
Another 500 balls, imported from India, were recovered from a handful of small independent sports shops in the county.
Devon trading standards director Steve Butterworth said: "We have nipped the problem in the bud. We think this is the first World Cup scam."
The balls, each with an England crest and called Cosmic or Elite, were being sold for between £5 and £8. Genuine Mitre balls are priced between £10 and £12.
An investigation was launched after Mitre said that it had received complaints about balls that had deflated after a few days.
Devon trading standards said it was not known how many balls could have been on their way into Britain, but it was suspected that the Indian source was looking to supply other outlets in the UK.
Mitre was "delighted" at the seizures. The firm said: "Counterfeit balls are poor quality, possibly made by an exploited, unskilled workforce and do not represent value for money."
Child labour in India is being put under the spotlight by an alliance of Indian sports goods manufacturers and the International Labour Organisation.
The groups are co-operating on a survey designed to establish the number of children working in the stitching of footballs.
Last year, a report from the charity Christian Aid said Indian children, some as young as seven, were routinely stitching footballs for export to Britain.
But the industry says campaigners have given a misleading picture. It strongly challenges the idea that contracting out football stitching has led to significant numbers of young children doing it for low pay and missing out on school.
It also argues that, unlike many other things children find themselves doing across south Asia, football stitching is not hazardous and is a useful skill for children to acquire.
However, with the image of the industry at stake, even ahead of the independent survey, there is already a move towards stitching centres that can be more easily monitored.